"""
ModelLoader - Smart Model Sharing between Spaces
Downloads models ONCE from gionuibk/NautilusModels and caches locally.
Subsequent calls use cached version (no re-download).
"""
import os
import json
from pathlib import Path
from typing import Optional, Dict, Any
from huggingface_hub import HfApi, hf_hub_download


HF_MODEL_REPO = "gionuibk/NautilusModels"
print("📦 ModelLoader Module Initialized") # Force Upload Hash Change
# Use HF's default cache - files are cached and only re-downloaded if changed
LOCAL_CACHE = None  # Let hf_hub_download use default cache


class ModelLoader:
    """
    Smart model loader with caching.
    - Downloads from HF only if not cached or file changed
    - Uses local cache for fast loading
    """
    
    def __init__(self, token: str = None):
        self.token = token or os.environ.get("HF_TOKEN")
        self.api = HfApi(token=self.token)
        self._manifest = None
        self._manifest_loaded = False
    
    def _load_manifest(self) -> Dict[str, Any]:
        """Load best_models.json manifest from HuggingFace (cached)."""
        if self._manifest_loaded:
            return self._manifest or {}
            
        try:
            manifest_path = hf_hub_download(
                repo_id=HF_MODEL_REPO,
                filename="best_models.json",
                repo_type="model",
                token=self.token
                # Uses HF default cache - fast if already downloaded
            )
            with open(manifest_path, 'r') as f:
                self._manifest = json.load(f)
            print(f"📋 Model manifest loaded: {list(self._manifest.keys())}")
        except Exception as e:
            print(f"⚠️ Could not load best_models.json: {e}")
            self._manifest = {}
        
        self._manifest_loaded = True
        return self._manifest
    
    def get_best_model(self, model_type: str, format: str = "onnx") -> Optional[str]:
        """
        Get path to the best model. Downloads once, then uses cache.
        
        Args:
            model_type: "deeplob", "trm", "lstm", etc.
            format: "onnx" or "pt"
            
        Returns:
            Local path to cached model file
        """
        manifest = self._load_manifest()
        
        if model_type not in manifest:
            print(f"⚠️ No model found for: {model_type}")
            return None
        
        model_info = manifest[model_type]
        
        # Prefer ONNX, fallback to PT
        if format == "onnx" and model_info.get("onnx_file"):
            filename = model_info["onnx_file"]
        elif model_info.get("pt_file"):
            filename = model_info["pt_file"]
            if format == "onnx":
                print(f"⚠️ ONNX not available for {model_type}, using PT")
        else:
            print(f"⚠️ No model file for {model_type}")
            return None
        
        # Download (or use cached version)
        try:
            local_path = hf_hub_download(
                repo_id=HF_MODEL_REPO,
                filename=filename,
                repo_type="model",
                token=self.token
            )
            # Dynamic Metric Logging
            metric_name = model_info.get("metric_name", "acc")
            metric_val = model_info.get("metric_value", model_info.get("accuracy", "N/A"))
            
            # Format value nicely
            if isinstance(metric_val, (int, float)):
                val_str = f"{metric_val:.4f}" if metric_val < 1 else f"{metric_val:.2f}"
            else:
                val_str = str(metric_val)
                
            print(f"✅ Model ready: {filename} ({metric_name}={val_str})")
            return local_path
        except Exception as e:
            print(f"❌ Failed to get {filename}: {e}")
            return None

    def check_for_update(self, model_type: str, current_path: str, format: str = "onnx") -> Optional[str]:
        """
        Check if a newer model is available.
        Returns new path if available, or None if no update.
        """
        # Force re-download of manifest (bypass internal flag, use cache control?)
        # hf_hub_download handles ETag check, so calling it again is cheap.
        try:
            old_manifest = self._manifest.copy() if self._manifest else {}
            
            # Re-fetch manifest (populating self._manifest with fresh data)
            self._manifest_loaded = False 
            new_manifest = self._load_manifest()
            
            if model_type not in new_manifest:
                return None
                
            model_info = new_manifest[model_type]
            
            # Determine filename
            if format == "onnx" and model_info.get("onnx_file"):
                filename = model_info["onnx_file"]
            elif model_info.get("pt_file"):
                filename = model_info["pt_file"]
            else:
                return None
                
            # Compare with current
            # If we don't have a current path, treat as update
            if not current_path:
                return self.get_best_model(model_type, format)
                
            if filename not in current_path:
                print(f"🆕 New model detected: {filename} (Replacing {os.path.basename(current_path)})")
                return self.get_best_model(model_type, format)
                
            return None
            
        except Exception as e:
            print(f"⚠️ Check for update failed: {e}")
            return None
    
    def get_model_info(self, model_type: str) -> Optional[Dict[str, Any]]:
        """Get metadata about a model."""
        return self._load_manifest().get(model_type)
    
    def list_available_models(self) -> list:
        """List all available model types."""
        return list(self._load_manifest().keys())


# Singleton instance
_loader: Optional[ModelLoader] = None


def get_model_loader() -> ModelLoader:
    """Get singleton ModelLoader."""
    global _loader
    if _loader is None:
        _loader = ModelLoader()
    return _loader


def get_best_model(model_type: str, format: str = "onnx") -> Optional[str]:
    """Get path to best model (downloads once, then cached)."""
    return get_model_loader().get_best_model(model_type, format)

def check_for_model_update(model_type: str, current_path: str, format: str = "onnx") -> Optional[str]:
    """Check and fetch update if available."""
    return get_model_loader().check_for_update(model_type, current_path, format)